Wi-Fi is a wireless standard for connecting electronic devices. Wi-Fi may also be known as IEEE 802.11. Generally, a Wi-Fi enabled device (also commonly referred to as a station), such as a personal computer, a tablet, a personal digital assistant, a video game console, a television, a smartphone, a digital media player, and the like may connect to a service provider when it is within range of a Wi-Fi network connected to the service provider. A typical access point (also commonly known as a hotspot) usually has a range on the order of 10s of meters when indoors and a greater range outdoors. Multiple overlapping access points may be used to provide coverage over larger areas.
In Wi-Fi, a communications channel is shared by stations under a mechanism referred to as a distributed channel access using a function called a distributed coordination function (DCF), which uses a carrier sense multiple access with collision avoidance (CSMA/CA). The DCF uses both physical and virtual carrier sense functions to determine the state of the communications channel (also commonly referred to as the medium). The physical carrier sense resides in a physical (PHY) layer and uses energy detection and preamble detection with frame length deferral to determine when the medium is busy. The virtual carrier sense resides in the media access control (MAC) layer and uses reservation information carried in a duration field of MAC headers announcing impending use of the medium. The virtual carrier sense mechanism is called the network allocation vector (NAV). In general, the medium is deemed to be idle only when both the physical carrier sense and the virtual carrier sense mechanisms indicate it to be so.